Stallergenes: Oralair: Very Positive 3-Year Results of the Long-Term Study

Very Positive 3-Year Results of the Long-Term Study Provide Confirmation of the Clinical Relevance of Oralair(R)

PARIS, December 7 - Stallergenes S.A. today announces the 3-year results of a
phase III clinical trial (VO53.06) to assess the long-term (sustained) effect
and disease modifier effect after discontinuation of treatment of its
sublingual grass pollen immunotherapy tablet, Oralair(R). This study is the
first ever pivotal study designed to be a long-term and disease modifier
trial from the outset.

The VO53.06 study is a randomized, double-blind,
placebo-controlled phase III trial conducted over 5 years, 3 years as a pre-
and coseasonal treatment regimen and the following 2 years without treatment.
It included 633 patients, aged 18 to 50 years, with grass pollen-related
allergic rhino-conjunctivitis, in 45 centers in 10 countries. The patients
were divided in two treated groups and one placebo group. In the two active
arms, there was no dose escalation and the daily dose was a 300 IR sublingual
immunotherapy tablet. In one active arm, the treatment started 4 months
before the pollen season, and in the other, 2 months before. The total
treatment duration for each study-year in all groups was 5 to 6 months up
until the end of the pollen season.

The sustained clinical efficacy as defined by EMEA[1]
guidelines is the measurement of treatment efficacy after 3 years. The
primary endpoint was the Average Adjusted Symptom Score (AASS)[2].

In the third year analysis, the two treated groups
demonstrated a statistically significant reduction of AASS in comparison with
placebo (p<0.0001) with a very large effect.

                 Relative differences versus placebo (season 3)

            2 months  4 months
     Mean     -36%      -34%
    Median    -50%      -48%

A reduction of 40% was achieved in the 2nd year and a
reduction of 30% in the 1st year (relative median differences versus
placebo). These results not only demonstrate the sustained clinical effect of
Oralair(R) administered using a pre- and coseasonal treatment regimen but
also suggest an increase in efficacy over the seasons.

In addition, each of the six individual symptom scores has
demonstrated a statistically significant improvement. All the outcomes
obtained in the secondary endpoints were statistically significant and
consistent with those of the primary endpoint.

Patient compliance was very satisfactory over the three
seasons and the overall tolerance was excellent.

In accordance with the recommendation of a board of
independent experts (Data and Safety Monitoring Board), the study will be
continued over the next 2 years in order to assess the disease modifier
effect (maintenance of therapeutic benefit after treatment discontinuation).

In addition to this long-term study, in 2009 Stallergenes
conducted a phase III one-season optimization study (VO60.08) with Oralair(R)
300 IR. This randomized, double-blind, placebo-controlled study was performed
without dose escalation and used a 2-month pre-seasonal treatment regimen. In
this trial, 180 patients were enrolled in each of the two arms. The analysis
on the primary endpoint did not reach a statistically significant difference,
although positive trends were demonstrated. Further in-depth analyses will be
performed, to identify likely methodological bias.

"We are very enthusiastic about the results of the VO53.06
study which far exceed our expectations. We will file for an extension of the
product's current labeling, as defined in the marketing authorization
recently obtained via a Mutual Recognition Procedure (MRP) in 23 European
countries. Such setbacks due to the VO60.08 study outcome can occur in any
large development program, and in no way call into doubt the overall findings
of the Oralair(R) program as a whole, which remain extremely consistent. The
development program, which focuses on the benefit to patients and fits
squarely with current cost-containment trends, confirms the relevance of
Stallergenes' strategic choices.

Our 2009 clinical news flow has been very dense and is not
over yet. There are still more results to come and more analyses to be
conducted. We will be delighted to present all these findings at an R&D day
to be held at the start of 2010." says Albert Saporta, Chairman and CEO of
Stallergenes.

ABOUT ORALAIR(R)

The Oralair(R) clinical development program has demonstrated
the short-term efficacy of the product at an appropriate dose of 300 IR
during the first season, through two clinical studies in adults and children
(VO34.04 and VO52.06).

Through a pharmacodynamics study (V056.07), Stallergenes
demonstrated that its immunotherapy tablet had an effect on symptoms from the
very first month of treatment, without the use of rescue medication and
irrespective of variable patient exposure to pollen.

The Oralair(R) development program, which has so far included
over 1,800 patients, makes the level of clinical evidence for this treatment
indisputable. This program, which was initiated in 2003 and is fully in line
with EMEA guidelines issued in 2008, will help immunotherapy tablets achieve
the same level of recognition as conventional pharmaceuticals.

From the outset, the Oralair(R) clinical development program
has addressed the key issues involved in grass pollen immunotherapy:

    - It answers the unmet needs of patients suffering from severe
      rhino-conjunctivitis caused by grass pollen, inadequately controlled
      using symptomatic treatments,

    - It favors compliance and cost-containment, through its pre-
      and coseasonal protocol (the treatment is taken for four months prior
      to the pollen season and then throughout it, for three consecutive
      seasons) rather than a perennial protocol (when the treatment is taken
      all year round),

    - Its active substance consisting of a set of five pollens
      corresponds to the epidemiological characteristics of patient exposure
      in Europe.

ABOUT THE STALAIR(R) PROGRAM

Stalair(R) is the pharmaceutical and clinical development
program for immunotherapy tablets being implemented by Stallergenes with a
view to obtaining marketing registrations for pharmaceutical products in
Europe and in other strategic markets.

Oralair(R) is the first project resulting from this program. A
Mutual Recognition Procedure has been completed. The results of a phase III
clinical study conducted in adults in the USA are expected in the coming
weeks.

A positive phase IIb/III study was completed for the dust mite
immunotherapy tablet, Actair(R) in allergic rhinitis in adults during the
first half of 2009. A pediatric phase III study has been launched.

The Bet v 1 tablet (birch pollen recombinant) has been the
subject of a positive phase IIb/III clinical trial conducted in allergic
rhinitis caused by birch pollen. A confirmatory phase III study is currently
being prepared with a view to EMEA registration.

The other allergens concerned by the program are ragweed for
the North American market and Japanese cedar pollen for the Japanese market.
Altogether, the program covers 80% of the epidemiology for all markets.

ABOUT STALLERGENES

Stallergenes is a European biopharmaceutical company dedicated
to immunotherapy treatments for the prevention and treatment of
allergy-related respiratory diseases, such as allergic rhinoconjunctivitis,
rhinitis and asthma. As of today, Stallergenes is the seventh-ranked French
pharmaceutical company. A pioneer and leader in sublingual immunotherapy
treatments, Stallergenes devotes 21% of its turnover, in gross terms, to
Research and Development and is actively involved in the development of a new
therapeutic class: sublingual immunotherapy tablets.

In 2008, Stallergenes had a turnover of 171 million euros and
more than 500,000 patients were treated with Stallergenes immunotherapy
products.

Euronext Paris (Compartment B)

SBF 120.

ISIN code: FR0000065674

Reuters code: GEN.PA

Bloomberg code: GEN.FP

Additional information is available at www.stallergenes.com

[1] European Medicines Agency

[2] AASS: Average Adjusted Symptom Score: A score taking into account the
daily rhino-conjunctivitis total symptoms score and rescue medication usage.

Contacts: Albert Saporta - Chairman and CEO, Tel.: +33-1-55-59-20-04, Christian Thiry - Financial Director, Tel.: +33-1-55-59-20-95, e-mail: investorrelations at stallergenes.fr. Press relations, Lise Lemonnier - Communication Manager, Tel.: +33-1-55-59-20-96, e-mail: llemonnier at stallergenes.fr. Investor and analyst relations, Lucile de Fraguier - Pavie Finance, Tel.: +33-1-42-15-04-39, e-mail: contact at pavie-finance.com